Mexico's President upended his country's politics. Will he be able to revolutionize ties with the U.S.?

He is an impatient man. When Mexican President Vicente Fox Quesada wants to make a phone call, he's as likely to dial himself as to wait for a secretary to do it. When he needs to talk to an adviser, he discards the standard chief-executive drill of sending a flunky to summon the official. Instead, boot heels clacking on the wooden floors of Los Pinos--the Mexican White House--Fox strides down the hall to the adviser's office himself.

In the ancient seat of empire that is Mexico City, the man at the top of the pyramid traditionally lets the world come to...